Abstract— <p>The safe treatment and reliable immobilization of waste generated during the reprocessing of spent nuclear fuel remain critical challenges for nuclear power. This study evaluates the feasibility of a plasma-based route that converts liquid reprocessing residues into chemically stable metal-oxide powders and then immobilizes these products into durable matrices suitable for long-term storage. The approach combines thermodynamic modeling with laboratory-scale experiments. Modeling was used to determine adiabatic combustion temperatures and equilibrium phase compositions for water–salt–organic feeds under plasma exposure. Experiments with a high-frequency plasma generator confirmed that, under optimized conditions near 1200°C, organic constituents are completely oxidized, and finely dispersed oxides are formed. The resulting powders include simple and complex oxides of iron, molybdenum, zirconium, neodymium, cerium, strontium, and yttrium; the phase balance depends on the plasma-cooling regime. Post-processing by gravitational and magnetic separation improves powder recovery and purity. For final conditioning, the oxides were incorporated into chloride-based melts, yielding dense, chemically and thermally stable solid forms after solidification. These results demonstrate that plasma treatment can integrate waste destruction, oxidation, and immobilization within a single technological workflow, reducing external heat demand and enabling robust products for storage or further use. The findings provide an engineering basis for scaling plasma systems for radioactive-waste management with an emphasis on safety, efficiency, and sustainability.</p>